DESCRIPTION: Aim 1 defines the microsurgical anatomy of human extraocular muscle that is needed for erbium laser procedure development. Aim 2 represents a design/development phase in adapting a commercial erbium laser for the purpose of selective weakening of extraocular muscle. Aims 3 and 4 use a rabbit model to develop laser applications specific for the targeted removal of a longitudinal muscle strip and denervation of selected segments of extraocular muscle. Aim 5 applies the targeted muscle compromise procedures developed in the rabbit to a subhuman primate model in which both muscle morphology and quantitative eye movement behavior can be tightly correlated. Aim 6 represents human pilot studies needed for design of clinical trials for the therapy developed in this proposal.